The present invention relates to a vibrator for a viscosimeter having a resonator fixed at two spaced points within a casing. One end of the resonator is adapted to extend from the casing to make contact with the liquid while the other end is surrounded by a pick-up coil adapted to set the oscillation of the resonator. The central part of the resonator comprises an exciting magnetostrictive bar.
Known supersonic torsion resonators or vibrators of this type, are used for continuous measurement of the viscosity of the liquid and consist of a half-wave resonator, fixed at its center so that one free end is in contact with the liquid to be measured. The other end serves for excitation and for picking up the oscillation of the resonator. Another known device, uses a torsion resonator, the length of which is equal to a half-wave or a multiple of a half-wave of the torsion oscillations in the respective material being measured. The resonator of this latter device is fixed at one nodal point and excited by a tangentially fixed supersonic logitudinally oscillating transducer in the oscillation node. A pick-up transducer is also tangentially fixed and stacked about 180.degree. with respect to the exicting transducer. These devices have the drawback that the tuning of both halves of the resonator, the Q of which is very high, is rather troublesome.
Other methods, which have attempted to eliminate these drawbacks present a great deal of difficulty in their construction and in their connection, particularly when applied in explosive or chemically aggressive and dangerous media. Such attempts to eliminate the drawback have used, for instance, the excitation simultaneously of both halves of the resonator.
Another drawback of the known devices is the limited mechanical resistivity of the construction, particularly for the measurements of flowing liquids the stream of which is not exactly laminar or linear. The influence of the electric or magnetic field of the exciting pulse, created by the flowing liquid, on the picked up electrical signal acts disturbingly in the measurement circuit.
Still further, in torsionally oscillating resignators, wherein magnetostriction phenomena is used for exciting torsional oscillations and wherein scanning is carried out on the basis of Weidemann's phenomenon in case of fixation at one nodal point of resonator oscillations, the amplitude/frequency is represented by two expressive maxima corresponding to the first harmonic of resonant frequencies of both the torsional and longitudinal wave, excited by the resonator. Therefore, it is impossible to achieve an electrical evaluation, by means of a pulsing excitation of the resonator, since on the scanning coil there are obtained voltages corresponding to both the longitudinal and torsional free oscillations of the resonator.
It is, therefore, the object of the present invention to reduce the drawbacks, enumerated above, in the use of the known torsion resonators and vibrators, and to produce a torsion vibrator for a supersonic viscosimeter which is simple in construction and use and which is highly effective.